The need for low-cost photonic devices has stimulated a significant amount of research in silicon photonics. Although silicon photonics is less well-developed as compared to III-V technologies, it has the potential to make a huge impact on the optical communications industry and in many other photonic applications. Silicon is transparent in the standard ITU optical communication bands, which makes silicon the material of choice for passive and active optoelectronic devices.
Microspheres have been gaining an important place in the optical micro-cavity resonator community due to their high quality factor morphology-dependent resonances (MDRs). Silicon microspheres with high quality factors MDRs are used for resonant detection and filtering of light in the near infrared. The light is coupled to the silicon microsphere with optical fiber half couplers in the near-IR. The observed MDRs have quality factors of 100,000. The experimentally measured quality factors are limited by the sensitivity of the experimental setup; however, the microsphere quality factor is several magnitudes of order higher than current micro-ring resonators.
These optical resonances provide the necessary narrow line width that is needed for high-resolution optical filtering applications, Raman lasers, modulators, and CMOS-compatible detectors in the near-IR. The silicon microsphere shows promise as a building block for silicon micro-photonics, a complementary technology to the already well established CMOS microelectronics technology, for the realization of future micro-electro-photonic integration. Numerous potential applications have been realized by using microspheres, such as: micro-lasers, channel dropping filters, optical switching, ultrafine sensing, displacement measurement, rotation detection, high-resolution spectroscopy, and Raman lasers.
Biochemical warfare has led to the need for early warning devices which can alert the warfighter of impending biochemical threats. A need exists for a reliable and reusable compact system, such as a microsphere-based system, that can detect the presence of biochemical agents with low false positive results.